Sand casting of lightmetals has been a process that has been done for a long time. To form a sand casting, sand is mixed with a binder resin, a cavity is formed within a block of this sand-binder combination, and molten metal is poured into the cavity to form a molded metal part. There have always been problems with this method, including the production of dross and oxidized state metals at the surface, along with all the problems of what to do with the sand after the casting has been made. Disposal of hundreds of pounds of sand for each casting is becoming a bigger and bigger problem. Because each casting mold, for example, an engine block, is used only once, six hundred pounds of sand need to be disposed of.
In addition, another problem arises because delivery of the molten metal is a relatively slow process into the sand cast mold because of turbulence issues, i.e. oxide problems need to be alleviated for faster delivery times. In yet another aspect of the conventional sand-cast method, cooling occurs relatively slowly, which reduces cycle time.
Many industries utilize sand casting for production of their parts, and they just live with the issues that are discussed hereinabove when making their production pieces. One such industry, i.e. the automobile industry, would benefit greatly from a reduced cycle time, mold weight reduction to alleviate disposal, and a reduced cycle time, in order to speed up production. Currently, lightmetals have become used more and more in the production of automobiles, in order to achieve better fleet mileages.
For the past several decades, automobile companies in the United States have been attempting to make fuel-efficient vehicles with reduced weights in order to provide environmentally friendly vehicles. A weight reduction in their vehicles is necessitated to reduce the fuel consumption required by these vehicles. It is desirable for American automobile companies to achieve better fuel economy and emission-free automobiles.
Lower fuel consumption regulations have been incorporated into governmental and industry changes that are desirable. As the most popular vehicles are large SUV's and trucks, which do not easily lend themselves to weight reduction, those weight reductions come through new designs and lightweight material substitutions, and not simply through the marketing of smaller, lightweight vehicles. It is, therefore, a goal of American automobile companies to produce desirable vehicles with a substantially reduced weight, utilizing recyclable materials, and exhibiting fuel efficiency and reduced emissions from the power trains. As energy prices are trending upward sharply, cost and weight reduction shall be urged forward by economic pressures, along with the United States Federal Government specifying fuel economy and emissions reduction targets in both passenger and light-trucks/SUVs.
One of the largest weight components of a vehicle is the engine block. Traditionally made of cast iron, there is an opportunity for a materials substitution to achieve weight reduction without sacrificing any of the performance. In the past, new materials that have been investigated included lightmetals and plastics. By way of historical perspective, in 1981, the average vehicle had 650 pounds of iron castings. By contrast, in 1995, iron consumption had declined to 350 pounds and is forecasted to reach only 215 pounds per vehicle by the year 2005. For a limited number of applications, the utilization of lighter materials, such as aluminum and plastic or composite polymer-based materials, currently meet the requirements of automotive companies for strength and durability. Aluminum applications have continued to grow until there is now over 350 pounds per average vehicle of aluminum parts.
Magnesium is one-third lighter than aluminum, while retaining the strength, wear and durability qualities needed by the automotive industry. Consequently, magnesium, or its alloys, is seen as the preferred new lightweight material to be utilized. Under certain manufacturing circumstances, though, magnesium can burn and is considered dangerous in certain applications and processes.
In order to provide safe processing of magnesium, conventional magnesium parts have been made by die castings. The industry is now looking for innovative non-die casting processing methods, especially for cold stamping or forming and low temperature low-pressure sand casting of magnesium. For the industry to review such non-die casting processes, there is a need for more of those innovative processes to be initiated. In fact, the automobile industry has identified potential die cast magnesium components which total about 250 pounds per vehicle. If engine blocks and large structural parts could be made of magnesium, there may be an additional 250 pounds per vehicle which can be made in non-die casting processes for large structural castings while still maintaining strength and durability requirements.
With the use of aluminum castings and plastics approaching a point of diminishing return from a cost-benefit perspective, magnesium or its alloys may become a major factor in the material selection process for automotive components and castings. Therefore, not only should one expect the use of magnesium die castings to grow in volume, but alternative casting processes can open the potential for magnesium components that heretofore were unable to be processed with die casting. Conventional metal die castings of lightmetals, such as aluminum, magnesium and their alloys, provide a greater opportunity for oxide formation on the surface of the molten magnesium.
In order to capture the attention of the automobile industry, it is always preferable to provide new manufacturing methods that have a low initial cost with high production rates, including a low cycle time. It is especially desirable if the new manufacturing method is amenable to the retrofitting of existing foundry equipment. When considering such a method, it should also be inexpensive to operate and to maintain.
A further advantage could be realized if the sand molds that are used in traditional sand castings for aluminum could be modified in order to reduce the amount of sand. Reclamation is needed when a mold has been utilized and must be recycled, and this reclamation process is time consuming and expensive. Therefore, there would be an advantage to reduce the amount of sand in each mold, as well as to provide porosity for the utilization of heat transferring gases which may be included. This “fast cast” system would be desirable for all lightmetal automotive applications as they generate the least amount of waste. This resulting lightmetal casting would achieve yet another advantage because it also needs to have a good molecular structure in order to provide for high quality castings that will be suitable for use in non-die casting component applications.
In these regards, the present invention provides a new method, machine, and precision sand cast mold which shall be advantageous in the automobile industry for non-die casting processed magnesium lightweight automobile and truck components.